1. Field of the Invention
The present invention relates to an image creating method and apparatus for creating an image of a liquid-object model which virtually represents a liquid object set in a three-dimensional virtual space. The invention also relates to a recording medium for recording a program implementing the above-described image creating method and to a video game machine.
2. Description of the Related Art
Conventionally, many game systems have been proposed: for example, a system consisting of a home-use game machine and a television monitor; and a system consisting of a commercial-use game machine, such as a personal computer or a workstation, a display unit, and a sound output unit.
Both types of systems are formed of a controller operated by a player, a recording medium on which a game program is recorded, a central processing unit (CPU) for controlling the generation of sound and images based on a game program, a processor for generating images, a processor for issuing sound, a monitor for displaying images, and a speaker for outputting sound. The above-described recording medium may include a CD-ROM, a semiconductor memory, or a cassette having a built-in semiconductor memory.
In the above types of game systems, a video game in which a liquid-object model virtually representing a liquid object, such as a sea or a river, is displayed on a monitor, for example, a fishing video game, may be considered. In this case, a liquid-object model is three-dimensionally formed by using polygons, and a texture representing, for example, a sea, is mapped on the individual polygons, thereby displaying the resulting model on a monitor.
In displaying such a model, there is a demand for realistically representing a virtual liquid object, such as the swell of waves and the flow of water, by suitably forming a liquid-object model by using polygons.
Accordingly, in view of the above background, it is an object of the present invention to provide an image creating method and apparatus for realistically representing a virtual liquid object by using a simple liquid-object model consisting of a plurality of polygons, and also to provide a recording medium for recording a program implementing the above image creating method and a video game machine.
In order to achieve the above object, according to one aspect of the present invention, there is provided an image creating apparatus for rendering a liquid-object model which virtually represents a liquid object set in a three-dimensional virtual space. The image creating apparatus includes a display unit. A first polygon storage unit stores at least one polygonal-prism liquid-object polygon set which consists of a plurality of polygons and which forms the liquid-object model, a lateral surface of the polygon set being arranged in a direction intersecting a line from a predetermined viewpoint. A first texture storage unit stores a liquid-object texture to be mapped on the polygons of the liquid-object polygon set. A first polygon-coordinate processing unit tilts a longitudinal dimension of the liquid-object polygon set in a predetermined direction with a predetermined amplitude with respect to a set position. A rendering processing unit displays the liquid-object model on the display unit by mapping the liquid-object texture on the polygons of the liquid-object polygon set.
With this arrangement, a liquid-object model is suitably displayed by a simply constructed liquid-object polygon set.
The aforementioned first polygon storage unit may store a plurality of the liquid-object polygon sets which are sequentially arranged along the line from the viewpoint.
Accordingly, since a plurality of the liquid-object polygon sets are displayed along the line from the viewpoint, the depth of the virtually displayed liquid-object is added, and the virtual liquid-object is more realistically displayed.
The first polygon-coordinate processing unit may rotate the liquid-object polygon set around an axis intersecting the line from the viewpoint with respect to the set position.
With this arrangement, the liquid-object texture is rotated on the display unit. Thus, it appears to the viewer that the liquid-object texture is rotated, thereby more realistically displaying the virtual liquid-object.
The above-described image creating apparatus may include: a second polygon storage unit for storing at least a spray polygon which forms a spray model virtually representing spray of the liquid object; a second texture storage unit for storing a spray texture representing the spray model; and a second polygon-coordinate processing unit for enlarging and reducing dimensions of the spray polygon over time within a predetermined range. The rendering processing unit may display the spray model on the display unit by mapping the spray texture on the spray polygon.
With this configuration, it is possible to suitably display the spray of the liquid object.
The aforementioned image creating apparatus may further include: a third polygon storage unit for storing at least one quadrilateral wake polygon which forms a wake model virtually representing wake of the liquid object and which has a pair of first sides intersecting the line from the viewpoint and a pair of second sides orthogonal to the first sides; a third texture storage unit for storing a wake texture representing the wake model; and a third polygon-coordinate processing unit for enlarging dimensions of the first sides and also reducing dimensions of the second sides with a lapse of time while fixing positions of the second sides. The rendering processing unit may display the wake model on the display unit by mapping the wake texture on the wake polygon.
With this configuration, the wake of the liquid-object can be suitably displayed on the display unit.
The above-described liquid-object model may virtually represent a sea wave, in which case, a virtual wave can be realistically displayed on the display unit.
According to another aspect of the present invention, there is provided an image creating method for rendering a liquid-object model which virtually represents a liquid object set in a three-dimensional virtual space. The image creating method includes the steps of: storing at least one polygonal-prism liquid-object polygon set which consists of a plurality of polygons and which forms the liquid-object model, a lateral surface of the polygon set being arranged in a direction intersecting a line from a predetermined viewpoint; storing a liquid-object texture to be mapped on the polygons of the liquid-object polygon set; tilting a longitudinal dimension of the liquid-object polygon set in a predetermined direction with a predetermined amplitude with respect to a set position; and displaying the liquid-object model on a display unit by mapping the liquid-object texture on the polygons of the liquid-object polygon set.
With this arrangement, it is possible to realistically display the virtual liquid object by a simply constructed liquid-object polygon set on the display unit.
According to still another aspect of the present invention, there is provided a recording medium for recording an image creating program used for rendering a liquid-object model virtually representing a liquid object set in a three-dimensional virtual space. The image creating program includes: a providing step of providing at least one polygonal-prism liquid-object polygon set which consists of a plurality of polygons and which forms the liquid-object model, a lateral surface of the polygon set being arranged in a direction intersecting a line from a predetermined viewpoint; a providing step of providing a liquid texture to be mapped on the polygons of the liquid-object polygon set; a tilting step of tilting a longitudinal dimension of the liquid-object polygon set in a predetermined direction with a predetermined amplitude with respect to a set position; and a mapping step of mapping the liquid texture on the polygons of the liquid-object polygon set.
By reading the recording medium by a computer and executing the above-described program, the foregoing steps are implemented. This enables the virtual liquid object to be realistically displayed on the display unit by using the simply constructed liquid-object polygon set.
According to a further aspect of the present invention, there is provided a video game machine including an image creating unit, which is formed by the above-described image creating apparatus, for rendering a liquid-object model which virtually represents a liquid object set in a three-dimensional virtual space. An externally operable operation unit outputs an operation signal according to an operation state. A viewpoint-line changing unit changes a viewpoint-line direction according to the operation signal.
With this configuration, the liquid-object model can be suitably displayed on the display unit according to the viewpoint-line direction.